Postirradiation long-range energy transfer in a single crystal of cytosine monohydrate: an EPR study.

Thiocytosine molecules incorporated in the cytosine monohydrate crystal lattice act as traps for both electrons and holes. The radiation-induced cytosine ion radicals, C(+) and C(-), release their charge upon heating. The excess electrons and holes migrate long distances in the crystal lattice. The migration of holes has been demonstrated by the postirradiation, thermally activated accumulation of thiocytosine cation radicals, T(+), and the migration of electrons by formation of the S-centered radicals of an anionic nature. It is estimated that the migration length of the holes is at least 30 interbase distances, and the migration length of the electrons is more than 100 interbase distances. The selective formation of the cationic and anionic trap radicals, depending on the trap concentration, is discussed in terms of differences between the migration of electrons and holes.